We use the Issuer field in the SAML authn request to lookup the partner service provider configuration by its name.
The Issuer field and PartnerServiceProviderConfiguration.Name must be an exact match.
Please double check that the name included in the exception and the configured name match exactly including any trailing slashes etc.
Also, setting the configuration once at application start-up is the correct approach. Make sure it isn’t being set anywhere else in the application.
If there’s still an issue, please enable SAML trace and send the generated log file as an email attachment to support@componentspace.com mentioning your forum post.